#include<stdio.h>

int main()
{
	char murderer = 'A';
	for(murderer = 'A'; murderer <= 'D'; murderer++)
	{
		if((murderer != 'A') + (murderer == 'C') + (murderer == 'D') + (murderer != 'C') == 3)
		{
			printf("%c", murderer);
		}
	}
	
	return 0;
}
